Name:	bsf_FederaHomeLoanBankAdvancesLetterOfCreditDisclosuresMaximumAmountAvailable
Namespace Prefix:	bsf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the fixed charge coverage ratio required for the notes payable.

No definition available.

Name:	bsf_NotesPayableFixedChargeCoverageRatio
Namespace Prefix:	bsf_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

Represents the maximum classified asset ratio which is a requirement for the notes payable.

No definition available.

Name:	bsf_NotesPayableMaximumClassifiedAssetRatio
Namespace Prefix:	bsf_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Represents the maximum loan to value ratio required for the notes payable.

No definition available.

Name:	bsf_NotesPayableMaximumLoanToValueRatio
Namespace Prefix:	bsf_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

Represents the Tier 1 leverage ratio required for the notes payable.

No definition available.

Name:	bsf_NotesPayableTier1LeverageRatio
Namespace Prefix:	bsf_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Amount of advances from Federal Home Loan Bank (FHLBank) maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601